import sys


def main():
    LargestProduct = -sys.maxsize - 1
    number = input().strip()
    for i in range(len(number) - 12):
        product = 1
        for j in range(13):
            product *= int(number[i + j])
        if product > LargestProduct:
            LargestProduct = product
    print(LargestProduct)


if __name__ == '__main__':
    main()
